Balloon catheters have been devised for use in various medical procedures, including angioplasty and balloon expandable stent/stent graft (implant) delivery. Commonly, a guidewire introduced percutaneously into the patient's vascular system advances via steering to the site of a stenosis. A dilatation balloon on the catheter is advanced over the guide wire until the balloon is positioned within the stenosis (which makes it desirable to provide the balloon with a particularly low profile, yet with adequate strength to be pushed through the vasculature). On inflation, the balloon compresses the stenosis by dilatation of the blood vessel to re-establish a more adequate blood flow path past the stenosis. To facilitate even compression pressure distribution along the length of the stenosed lesion, it is a clinical preference that the dilation balloon be sized and centered relative to the stenosis so as to fully engage the lesion.
Balloon dilation catheters have also been utilized in balloon expandable implant delivery in which the implant is disposed about the balloon and inflated into place at the stenosis. Catheter operators seek accurate deployment of the implant directly on the diseased tissue of the vessel in order to avoid stent migration to either side of the diseased tissue thereby avoiding or minimizing the chance of leaving some of the diseased tissue untreated. Accurate deployment also desirably avoids adversely affecting healthy tissue.
Implant misplacements may occur because of specific inflation dynamics experienced by the expandable balloon when deploying the implant. Many balloon expandable implant delivery catheters inflate the balloon preferentially from the proximal end of the balloon (and may suffer from the inability to transmit inflation fluid from the proximal to the distal end as a result of the placement of the compressed or unexpanded implant over the balloon). During inflation, the expanding balloon may form an asymmetrical growth or inflation wave that may be said to drive or plow the implant so that it opens progressively from one end to the other along the front of the inflation wave. The wave may sometimes cause the implant to disengage prematurely from the balloon, and may also cause a deploying implant to displace longitudinally away from its intended delivery site, thereby potentially ineffectively treating the diseased lesion within the patient's vasculature. This premature deployment is often described as “watermelon seeding.” Accuracy of positioning is also important for stents and stent grafts, as missing the target can have deleterious consequences.
Accordingly, a need is identified for a balloon catheter that may be inflated in a preferential manner and with better regulation in order to facilitate the proper delivery of a stent, stent graft, or the like, yet without sacrificing the desire for a low-profile arrangement.